One of the key components of any computer system is a place to store data. Computer systems have many different places where data can be stored. One common place for storing massive amounts of data in a computer system is on a disk drive. The most basic parts of a disk drive are a disk containing the recording medium that is rotated, an actuator that moves a transducer to various locations over the disk, and electrical circuitry that is used to write and read data to and from the disk. The disk drive also includes circuitry for encoding data so that it can be successfully retrieved and written to the disk surface. A microprocessor controls most of the operations of the disk drive as well as passing the data back to the requesting computer and taking data from a requesting computer for storing to the disk.
The transducer is typically housed within a small ceramic block of material, commonly referred to as a slider. The slider is passed over the disk in a transducing relationship with the disk. The transducer can be used to read information representing data from the disk or write information representing data to the disk. When the disk is operating, the disk is usually spinning at relatively high RPM. These days common rotational speeds are 7200 RPM. Some rotational speeds are as high as 10,000 RPM. Higher rotational speeds are contemplated for the future. These high rotational speeds place the slider in high air speeds. The slider is usually aerodynamically designed so that it flies over the disk. The best performance of the disk drive results when the transducer is flown as closely to the surface of the disk as possible. Today's slider is designed to fly on a very thin layer of gas or air. In operation, the distance between the slider and the disk is very small. Currently "fly" heights are about 1-2 micro inches. In some disk drives, the transducer does not fly on a cushion of air but rather passes through a layer of lubricant on the disk.
Information representative of data is stored on the surface of the disk. Disk drive systems read and write information stored on tracks on disks. Transducers, in the form of read/write heads, located on both sides of the disk, read and write information on the disks when the transducers are accurately positioned over one of the designated tracks on the surface of the disk. The transducer is also said to be moved to a target track. As the disk spins and the read/write head is accurately positioned above a target track, the read/write head can store data onto a track by writing information representative of data onto the disk. Similarly, reading data on a disk is accomplished by positioning the read/write head above a target track and reading the stored material on the disk. To write on or read from different tracks, the read/write head is moved radially across the tracks to a selected target track. The data is divided or grouped together on the tracks. In some disk drives, the tracks are a multiplicity of concentric circular tracks. In other disk drives, a continuous spiral is one track on one side of a disk drive. Servo feedback information is used to accurately locate the transducer. The actuator assembly is moved to the required position and held very accurately during a read or write operation using the servo information.
One of the most critical times during the operation of a disk drive is just before the disk drive shuts down. The slider is typically flying over the disk at a very low height when shutdown occurs. In the past, the slider was moved to a non data area of the disk where it literally landed and slid to a stop resting on the surface of the disk. Problems arise in such a system. When disks are formed with a smooth surface, stiction may result between the slider and the disk surface. In some instances, the force due to stiction is large enough to rip the head away from the suspension. Amongst the other problems was a limited life of the disk drive. Each time the drive was turned off another contact-start stop cycle would result. When shutting down a disk drive, several steps are taken to help insure that the data on the disk is preserved. In general, the actuator assembly is moved so that the transducers do not land on the portion of the disk that contains data. There are many ways to accomplish this. A ramp near the edge of the disk is one design method that has gained industry favor more recently. This method is commonly referred to as ramp load. Disk drives with ramps are well known in the art. U.S. Pat. No. 4,933,785 issued to Morehouse et al. is one such design. Other disk drive designs having ramps therein are shown in U.S. Pat. Nos. 5,455,723, 5,235,482 and 5,034,837.
Typically, the ramp is positioned to the side of the disk. A portion of the ramp is positioned over the disk itself or adjacent to the disk. In operation, before or just after power is actually shut off, the actuator assembly swings the suspension or another portion of the actuator assembly up the ramp to a park position at the top of the ramp. When the actuator assembly is moved to a position where parts of the suspension are positioned on the top of the ramp, the sliders do not contact the disk. Commonly, this procedure is known as unloading the heads. Unloading the heads helps to insure that data on the disk is preserved since, unwanted contact between the slider and the disk may result in data loss on the disk A feature is provided on the suspension or actuator assembly to ride up the ramp to lift the heads off the disk. This feature may generally be referred to as a load tang. In other drives, the ramp may be positioned such that the suspension rides up and down the ramp to unload and load the disk or disks of the disk drive.
Associated with each disk surface is a ramp. A load/unload structure must therefore be formed having multiple ramps which are registered to the disk surfaces of each disk in the disk stack. Many of the components of the drive are made from separate parts. For example, the disk stack is formed on a hub from a number of disks and spacers. Each disk and each spacer has a tolerance. The tolerances can stack up differently for each disk stack assembly. Similarly, there are stack up tolerances associated with other components made from separate parts, such as the load/unload mechanism, and the E-block which holds all the separate head gimbal assemblies.
Overcoming tolerance problems is a constant problem faced in designing and assembling disk drives. The placement of ramps near the disks is one area of the drive where potential tolerance mismatches may cause problems. The E-block can be formed of separate parts. The E-block holds all the transducing heads over the disk surfaces. The E-block is another potential problem with respect to stack up tolerances. When the E-block is moved to unload or load the heads onto the disks in the drive, three components meet. Each of the three may have a potential stack up tolerance mismatch with respect to the other components.
As a result of potentially having three separate components with separate stack up tolerances meeting, there is a possibility that tolerance mismatches would result in interference between components. For example, a suspension attached to an arm of the actuator may strike the end of a ramp rather than ride up the ramp surface. As a result, there is a need for a system which has some adjustability. This is further necessary in light of the fact that as interdisk spacing gets smaller, the tolerances associated with the disk stack are becoming tighter. In addition, the components are becoming much more sensitive to slight shock loading or to thermal effects. The sliders which contain a transducer are now smaller than ever before. Gimbal springs must allow for gimballing of the sliders and are therefore much more sensitive to slight shock loading. A slight shock load can effect a suspension so that the z-height may be off slightly. Similarly, small tilt angles can result in the arms of the actuator. Since the components are more sensitive to such changes, it is necessary to also allow for some adjustability in one or more components of the actuator. Lastly, the flying height of the slider is heavily influenced by the static attitude of the head.